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The Ihara expression for the generalized weighted zeta function of a finite simple graph
No full textapplication/pdfGraph zeta functions have two kinds of determinant expressions, the Hashimoto expression and the Ihara expression. The main theorem of the present article gives the Ihara expression for graph zeta functions with a certain generalized weight. It unifies all the Ihara expressions known for the existing zeta functions of finite simple graphs. (C) 2021 Elsevier Inc. All rights reserved.journal articl
大規模アンサンブルシミュレーションに基づく気候変動の不確実性を考慮した洪水リスクの評価
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdfこの数十年で、気候変動による異常気象とそれに起因する自然災害は、自然環境や私たちの生活に対する脅威の一つとして急速に関心を集めるようになった。こうした自然災害の中でも、洪水は世界的に頻発しており、世界各地で甚大な被害を引き起こしている。さらに、洪水による災害は、将来的により頻繁に発生し、より深刻な被害を発生させると考えられている。特に河川の氾濫原の住民や、早期の洪水警報システムが整備されていない地域で生活している人々は、洪水による影響を最も大きく受ける。日本では、近年、短時間での極端豪雨による洪水氾濫が頻発し、大きな被害をもたらしている。顕著な例として、2016年8月には北海道で大規模な洪水が発生した。また2019年10月には日本の中部から東北地方にかけて多数の河川で深刻な洪水と地すべりが発生した。これらの被害により、尊い人命と資産が失われた。日本の北端に位置する北海道では、過去には1981年8月、近年では2016年8月の洪水において、石狩川流域は甚大な被害を受けた。石狩川流域内は石狩平野が大部分を占め、その中流域から下流域にかけては北海道のみならず全国で最も生産性の高い農業地域となっていることから、北海道の社会経済的発展に重要な役割を果たしている。そのため、本研究では、北海道の石狩川流域を対象とし、気候変動による極端豪雨の降雨量の変化と、それに伴い大規模洪水を引き起こす河川流量の変化を推定することを目的としている。石狩川流域とその主要な支川における不確実性を考慮した極端豪雨のデータとして水平解像度5kmの大量アンサンブル降雨情報(d4PDF)を用いた。また、石狩川とその主要支川の河川流量の推定には統合洪水解析システム(IFAS)を用いた。さらに、千歳川流域の洪水氾濫の変化についても、d4PDFと降雨-流出-氾濫モデル(RRI)を用いることで、石狩川からの背水影響を考慮した氾濫計算を行った。本研究では、豪雨と洪水の評価に高解像度の大規模アンサンブル気候シミュレーションを使用したことが特徴である。これは、100年に一度以上の低頻度で生起する極端豪雨と、それによって発生する深刻な洪水を予測することができる。さらに、大規模アンサンブル気候シミュレーションを用いることにより、極端豪雨時の降雨の不確実性を適切に評価することができる。本研究において判明した結果は、河川流域管理、特に氾濫原における洪水被害の軽減といった気候変動への適応策に役立てることが期待される。In recent decades, extreme weather events associated with climate changes have rapidly become one of the global concerns threatening natural environments and human life. Floods are the most frequent type of natural disaster on earth, causing massive damage all over the world. Flood disaster is considered to become more frequent and higher intensity in the future. In particular, people who live in floodplain areas, or lack early flood warning systems are the most affected by flooding. In Japan, flood inundation disasters due to short-term extreme rainfall have occurred frequently and caused considerable damage in recent years. Notable severe flood events in recent years in Japan can be mentioned as the large-scale flood event in August 2016 in Hokkaido, or severe flooding and landslides occurred in many river basins in central-northern parts of Japan in October 2019, causing great loss of life and property. The northernmost Japanese island, Hokkaido has recorded severe floods and caused massive damage, such as the flood event in August 1981, and recently in August 2016. The Ishikari River basin plays a vital role in the socio-economic development of Hokkaido. The Ishikari Plain occupies most of the basin’s area and is located around the central and downstream basin area, which is the most productive agricultural area not only in Hokkaido, but also entire Japan. Therefore, this study aims to investigate the change in extreme rainfall and severe floods associated with climate change, choosing the Ishikari River basin, Hokkaido, Japan as a case study. Change in extreme rainfall and river floods in the Ishikari River basin, as well as in its main sub-basins is evaluated using the Integrated Flood Analysis System (IFAS) coupled with the large-ensemble rainfall dataset with a super high-resolution of 5 km as an input data to the model. In addition, change in flood inundation in the Chitose River basin, a tributary of the Ishikari River is also evaluated using the Rainfall–Runoff– Inundation (RRI) model and a large-ensemble rainfall dataset of 5 km (d4PDF). Owing to the topographical characteristics of its low-lying area, the Chitose River basin is frequent affected by backwater from the Ishikari River and experiences severe flood inundation. The remarkable point of this study is to use the large-ensemble and super high-resolution climate simulations for extreme rainfall and severe floods assessment. It could predict extreme rainfall and severe flood events with return periods equal to or larger than 100 years. Simulation with large ensemble members could properly verify the uncertainty in the estimation of the probability of extreme events. The results of this study are expected to provide useful information for river basin management, particularly for climate change adaptation and flood damage mitigation in floodplain areas.doctoral thesi
金属粒子を担持した酸化亜鉛粒子の生成と有機染料分解機能の評価
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdf既存の排水処理方法では、有機汚染物質が分解されず、二次汚染になる問題がある。したがって、本研究では、有機染料の分解のために酸化亜鉛(ZnO)光触媒による酸化処理の研究を行った。しかし、ZnOのような光触媒は、励起された電子-正孔対の速い再結合により触媒活性が制限されることと、使用後の回収が困難であることから再利用が制限されるという欠点がある。このような欠点を補完するために、電子シンクの役割をするAuまたはAg粒子の担持と、磁性を持つFe3O4との複合化を行った。第2-3章では、超音波噴霧熱分解(ultrasonic spray pyrolysis; USP)法を用いてAg/ZnOとAu/ZnO粒子を生成した。生成粒子のXRD結果では、ZnOの結晶ピークとAg又はAuの結晶ピークが観察された。TEMとEDX画像から粒子全体に分散しているダークスポットがAgまたはAuナノ粒子に該当することを確認した。また、ローダミンB (Rhodamine B; RhB)を有機汚染物のモデル物質として用いた光分解実験の結果から、生成したAu/ZnOとAg/ZnO粒子が純粋なZnO粒子よりも高い光触媒活性を持つことが分かった。特に、原料溶液として硝酸亜鉛2.5 mass%と塩化金酸0.1 mass%や硝酸銀0.2 mass%を用いて生成したAu/ZnO及びAg/ZnO粒子は、純粋なZnO粒子と比べて反応速度定数がそれぞれ約4倍、8倍高かった。得られたAu/ZnOとAg/ZnO粒子のなかには、広く光触媒として用いられているTiO2粒子であるP25より高い光分解活性を表す粒子もあった。100 mLのRhB水溶液を使って粒子の最適な添加量を評価した結果、粒子を2 mgから10 mgまで添加することにより、触媒活性は比例して増加したが、より高い添加量では際立った向上はなかった。電子励起に重要な紫外線が粒子によって散乱されたためだと考えられる。また、生成された粒子は、光分解実験後に重力沈殿による回収が可能であり、光触媒活性の劣化が遅いことも観察された。第4章では、粒子をより簡単に回収するために、強磁性Fe3O4粒子とZnO粒子の複合化を試みた。最初に硝酸亜鉛と塩化鉄の混合溶液からUSP法によってシングルステップで生成した粒子では、目的生成物であるZnOとFe3O4の結晶ピークは観察されず、ZnFe2O4のピークのみ観察された。次に、共沈法で生成したFe3O4をクエン酸を用いて表面改質物質した後、USP法により生成したZnO粒子と複合化した場合、ZnOとFe3O4の結晶ピークと磁力による沈降分離の促進が観察された。しかし、複合化されていないZnO粒子と粒子の凝集も観察された。最後に、塩化鉄と硫酸鉄を原料として共沈法で生成したFe3O4粒子に、硝酸亜鉛と硝酸銀の混合溶液を用いて共沈法により複合化した粒子では、目的生成物であるZnO、Ag、Fe3O4の結晶ピークが観察された。光分解実験では、実質的なZnOの添加量が減少するため、ZnO/Fe3O4複合粒子の光分解特性は純粋なZnO粒子より悪かった。しかし、ZnO/Fe3O4/Ag複合粒子は、Fe3O4が含まれているにもかかわらず、純粋なZnO粒子よりも優れた光分解特性を発揮した。本研究では、実際の廃水による分解実験は実施してないが、生成した複合粒子の有機汚染物質の浄化可能性が確認された。第5章では、本論文の総括を行った。With existing wastewater treatment methods, there is a problem that organic pollutants are not decomposed and become secondary pollution. Therefore, in this study, a photocatalytic oxidation treatment was conducted for the decomposition of organic dyes. However, photocatalysts such as ZnO have the disadvantages that their catalytic activity is limited by the rapid recombination of excited electron-hole pairs and that their reuse is limited due to the difficulty of recovery after use. Therefore, Au and Ag, which act as electron sinks, were supported on the ZnO particles, and the composite was performed with Fe3O4 having magnetic properties. In Chapters 2-3, Ag/ZnO and Au/ZnO particles were generated using the ultrasonic spray pyrolysis (USP) method. In the XRD results, a ZnO crystal peak and an Ag or Au crystal peak were observed. From the TEM and EDX images, it was confirmed that the dark spots dispersed throughout the particles correspond to Ag or Au nanoparticles. In addition, as a result of photolysis experiments using Rhodamine B (Rhodamine B; RhB) as a model material for organic pollutants, the synthesized Au/ZnO and Ag/ZnO particles showed higher photolysis activity than pure ZnO particles generated by the USP method. In particular, the Au/ZnO and Ag/ZnO particles generated by adding 0.1mass% of HAuCl4 or 0.2mass% of AgNO3 to the 2.5mass% of Zn(NO3)2 aqueous solution showed reaction rate constants about 4 and 8 times higher than that of the pure ZnO particles, respectively. Among Au/ZnO and Ag/ZnO particles, some particles exhibited higher photodegradation activity than P25, which is a TiO2 particle widely used as a photocatalyst. As a result of evaluating the optimal amount of particles added using 100 mL of RhB aqueous solution, the catalytic activity increased from 2 mg to 10 mg in proportion to the addition of particles, but there was no obvious improvement in catalytic activity with more additions. It was also observed that the generated particles can be recovered by gravitational precipitation after the photodecomposition experiment, and the deterioration of photocatalytic activity is slow. In Chapter 4, a composite of ferromagnetic Fe3O4 particles and ZnO particles was attempted to recover particles more easily. First, in the particles generated from a mixed solution of zinc nitrate and iron chloride in a single step by the USP method, the crystal peaks of the target products ZnO and Fe3O4 were not observed, but only the peak of ZnFe2O4 was observed. Next, when ZnO particles produced by the USP method were combined with Fe3O4 produced by the coprecipitation method using citric acid as a surface modifier, the crystal peaks of ZnO and Fe3O4 and the promotion of sedimentation separation by magnetic force were observed. However, uncomposted ZnO particles and agglomeration of particles were also observed. Finally, Fe3O4 particles produced by coprecipitation using iron chloride and iron sulfate as raw materials were compounded by coprecipitation using a mixture of zinc nitrate and silver nitrate, and crystal peaks of ZnO, Ag, Fe3O4 were observed. In the photolysis experiment, the photodecomposition properties of the ZnO/Fe3O4 composite particles were worse than those of pure ZnO particles because the amount of ZnO added was substantially reduced. However, the ZnO/Fe3O4/Ag composite particles exhibited better photodegradation properties than the pure ZnO particles, even though they contained Fe3O4. In Chapter 5, the conclusion of this study was scrutinized.doctoral thesi
Two-Dimensional Full-Vectorial Finite Element Analysis of NRD Guide Devices
Get PDFapplication/pdfNonradiative dielectric waveguide (NRD guide) is a promising platform for realizing compact millimeter waveguide circuits. NRD guide devices have been simulated by several numerical simulation approaches so far and these approaches treat 3-D structure because electric and magnetic fields in NRD guides vary in whole directions. In this letter, we propose a 2-D full-vectorial finite element analysis for efficient simulation of NRD guide devices.journal articl
Investigation on the Power Factor of Skutterudite Sm-y(FexNi1-x)(4)Sb-12 Thin Films: Effects of Deposition and Annealing Temperature
Get PDFapplication/pdfFilled skutterudites are currently studied as promising thermoelectric materials due to their high power factor and low thermal conductivity. The latter property, in particular, can be enhanced by adding scattering centers, such as the ones deriving from low dimensionality and the presence of interfaces. This work reports on the synthesis and characterization of thin films belonging to the Sm-y(FexNi1-x)(4)Sb-12-filled skutterudite system. Films were deposited under vacuum conditions by the pulsed laser deposition (PLD) method on fused silica substrates, and the deposition temperature was varied. The effect of the annealing process was studied by subjecting a set of films to a thermal treatment for 1 h at 423 K. Electrical conductivity sigma and Seebeck coefficient S were acquired by the four-probe method using a ZEM-3 apparatus performing cycles in the 348-523 K temperature range, recording both heating and cooling processes. Films deposited at room temperature required three cycles up to 523 K before being stabilized, thus revealing the importance of a proper annealing process in order to obtain reliable physical data. XRD analyses confirm the previous result, as only annealed films present a highly crystalline skutterudite not accompanied by extra phases. The power factor of annealed films is shown to be lower than in the corresponding bulk samples due to the lower Seebeck coefficients occurring in films. Room temperature thermal conductivity, on the contrary, shows values comparable to the ones of doubly doped bulk samples, thus highlighting the positive effect of interfaces on the introduction of scattering centers, and therefore on the reduction of thermal conductivity.journal articl
Modeling of dowel action for cast-in and post-installed anchors considering bond property
No full textapplication/pdfIn reinforced concrete structures, cast-in anchors are applied to beam-column or slab-beam joints. Furthermore, in seismically strengthened structures, post-installed anchors are used to connect new members to existing members. These anchors are subjected to shear and tensile stresses during an earthquake. However, a mechanical model that can estimate the behavior of these anchors when subjected to combined stress has not yet been proposed. Therefore, in this study, various anchors were tested under combined stress conditions. The test parameters were the type of anchorage method, shape of anchor bolt, anchorage length, hole diameter of the drilling, type of adhesive, and tensile stress ratio. It was observed that the shear force of the post-installed anchors was larger than that of the cast-in anchors. Moreover, as the diameter of the hole increased, the shear force also increased. Subsequently, the mechanical model, which was proposed for a post-installed anchor in a previous study, was modified for application to various anchors. By considering the diameter of the hole in the bearing resistance and introducing the bond strength to catenary action, the test results of the various anchors could be reasonably estimated.journal articl
Silicon dissolution and morphology modification of NITE SiC/SiC claddings in pressurized flowing water under neutron irradiation
No full textapplication/pdfCladdings of silicon carbide (SiC)-based composites for light water reactors are expected to be a key component of accident-tolerant fuel technology for enhancing nuclear safety. Muroran Institute of Technology has developed technologies for producing SiC/SiC claddings by a nano-infiltration and transient eutectic phase (NITE) method in the MEXT-funded project named "SCARLET." As part of this program, neutron irradiation experiments were performed in a pressurized cooling water flow at the Halden Reactor in Norway. During the irradiation experiments, silicon dissolution from the SiC/SiC specimens was measured, and the relationship among the dissolution, properties of SiC/SiC claddings and reactor operating conditions was studied. The morphology of the SiC/SiC claddings was not significantly modified by the irradiation experiments; however, the joint parts were corroded and suffered damage. Observation of irradiated specimens and a rough estimate of the SiC dissolution rate under each irradiation condition indicated that the NITE SiC/SiC composite has potential as a structural material for pressurized water reactors (PWRs) that are operated under hydrogen water chemistry conditions. It is also shown that chemical-vapor-deposited (CVD)-SiC and other coating techniques are necessary for the realization of SiC reactor core. Joining and coating technologies were also tested, but appropriate methods could not be identified experimentally; thus, joining and coating techniques should be further developed. (c) 2021 Elsevier B.V. All rights reserved.journal articl
道路の耐久性向上に資する路床土の設計パラメータに関する研究
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdf本研究は，道路の耐久性の向上に資するために，土質条件や気象条件，荷重載荷条件を評価可能な路床土の設計パラメータを得る方法の提案を目指したものである．設計パラメータの検討対象は，「応力依存性」，「排水条件の影響」を考慮した変形係数であり，その評価および提案を行うために，複数の異なる地盤材料を用いた室内土質試験を実施した．「舗装設計に地盤工学の研究成果を十分に反映させ，舗装下の有効応力状態の理解を深めるための更なる研究が，将来の舗装工学を改善させるための基礎となる可能性がある」との指摘（Brown, S. F., 1996）を踏まえ，道路の耐久性向上を目指すためには，設計パラメータ取得の手段に精度の高い室内土質試験の適用が必要不可欠であると考えられる．そこで，本研究では，地盤工学会基準に定められている「繰返し三軸試験(JGS0542-2009)」（以下CTX試験）および「ベンダーエレメント試験(JGS0544-2011)」（以下BE試験）から得られるデータを用いるものとした．さらに，両試験の実施によって，変形係数Eの「応力依存性」と「排水条件の影響」を評価できることから，「ベンダーエレメント併用繰返し三軸試験（以下CTX-BE試験と称す）」を新たに開発した．この試験により，ベンダーエレメントを取り付けた供試体で，排水条件を変えたCTX試験の繰返し載荷中に，BE試験を数回実施することによりせん断剛性率Gと平均有効主応力σm’の関係を評価することができる．試験に用いた地盤材料として，物理指標の異なる8種の試料を用いてCTX-BE試験を行い，各試料の試験結果と既往の研究結果との比較により試験方法の妥当性を検証した．その後，得られたデータに基づいて，舗装設計に用いるための設計パラメータとなる非排水条件下の変形係数Euとポアソン比νuおよび，排水条件下の変形係数Edとポアソン比νdを求めた．さらに，EuおよびEdについて，平均有効主応力σm’と間隙比関数f(e)をパラメータとした推定式を導いた．以上より，路床土の排水条件を考慮した舗装構造設計に必要な変形係数とポアソン比を設定するための新しい手法を提案した．本研究は，近年の環境問題や様々な社会的要請を踏まえ，舗装構造設計における環境問題解決型研究と理論的舗装設計を連携させた取組みに位置づけられる．また，応力依存性と排水条件を考慮した路床土の設計パラメータとしての変形係数の設定方法を提案した研究成果は，その連携に大いに寄与するものであると考えられる．The purpose of this study is to propose a method for obtaining design parameters of subgrade soil that can evaluate soil conditions, meteorological conditions, and loading conditions in order to contribute to the durability of roads. The design parameters were examined for deformation modulus that considered "stress dependency" and "effects of drainage conditions", and soil testing were conducted using multiple different soil materials in order to evaluate and propose them. "Further research to fully reflect the research results of soil engineering in pavement design and deepen the understanding of the effective stress state under pavement may be the basis for improving pavement engineering in the future." Based on the indication of (Brown, SF, 1996), it is indispensable to apply a highly accurate soil testing as a means of acquiring design parameters in order to improve the durability of the road. Therefore, the data of "Cyclic triaxial test (JGS0542-2009)" (hereinafter CTX test) and "Bender element test (JGS0544-2011)" (hereinafter BE test) specified in the Japanese Geotechnical Society standards are used in this study. Furthermore, since the "stress dependency" and "effect of drainage conditions" of the deformation modulus E can be evaluated by conducting both tests, the "Cyclic triaxial test combined with Bender element (hereinafter referred to as CTX-BE test)" is newly introduced. In this test, the BE test was performed several times during the CTX test in which the drainage conditions of the specimen with the bender element were changed, and the relationship between the shear modulus G and the mean effective stress σm' was evaluated. The CTX-BE test was conducted using eight types of geomaterials with different physical indicators, and the validity of the test method was verified by comparing the trends of the data obtained from the test results of each sample with the results of previous studies. After that, based on the obtained data, the deformation modulus Eu and Poisson's ratio νu under undrained condition and the deformation modulus Ed and Poisson's ratio νd under drained condition, which are design parameters for use in pavement design, were discussed. Furthermore, for each of Eu and Ed, an estimation formula was derived with the mean effective stress σm' and the void ratio function f (e) as parameters. Based on the above results, a new method for setting the deformation modulus and Poisson's ratio required for pavement structure design considering the drainage conditions of the subgrade soil was proposed. Based on recent environmental problems and various social demands, this research is positioned as an initiative that links environmental problem-solving research in pavement structure design with theoretical pavement design. The research results that proposed a method for setting the deformation modulus as a design parameter for subgrade soil in consideration of stress dependency and drainage conditions are considered to greatly contribute to the cooperation.doctoral thesi
Learning Human Activities through Wi-Fi Channel State Information with Multiple Access Points
Get PDFapplication/pdfWi-Fi channel state information (CSI) provides adequate information for recognizing and analyzing human activities. Because of the short distance and low transmit power of Wi-Fi communications, people usually deploy multiple access points (APs) in a small area. Traditional Wi-Fi CSI based human activity recognition methods adopt Wi-Fi CSI from a single AP, which is not so appropriate for a high-density Wi-Fi environment. In this paper, we propose a learning method that analyzes the CSI of multiple APs in a small area to detect and recognize human activities. We introduce a deep learning model to process complex and large CSI information from multiple APs. From extensive experiment results, our method performs better than other solutions in a given environment where multiple Wi-Fi APs exist.特集departmental bulletin pape